Patent EA-001503-B1 (EA)
Title: Method for improving surface by laser treatment
Inventor: MCCAY THURMAN DWAYNE
IPC: B23K26/00
Filed: 1997-01-15
Abstract: 1. A method of controlling alloy formation in the surface region of a metal workpiece to a predetermined depth, comprising: a. applying a binder comprising an alloying precursor to the surface of a metal workpiece; b. irradiating the surface of the workpiece and the allowing precursor with a laser beam emitted from a laser delivery system at a sufficient power and for a sufficient duration to melt the surface of the workpiece and the precursor while moving the workpiece and the precursor relative to the laser beam through the use of a movement system; and c. measuring the temperature of the workpiece surface during irradiation; and d. controlling laser beam power In response to measured temperature in order to control the depth of alloying in the workpiece. 2. The method of claim 1, wherein the laser beam power is controlled by changing the pulse cycle of the laser. 3. The method of claim 1, further comprising the step of applying a reacting gas to the region of the workpiece being irradiated. 4. The method of claim 3, wherein said reacting gas is a reducing gas. 5. A method of controlling alloy formation in the surface region of a metal workpiece to a predetermined depth, comprising: a. applying a binder comprising an alloying precursor to the surface of a metal workpiece; b. irradiating the surface of the workpiece and the precursor alloy with a laser beam from a laser delivery system while moving the workpiece and precursor relative to the laser beam through the use of a movement system; and c. measuring emission spectra data from the laser surface interface; and d. transmitting emission spectra data to a feedback control system; and e. using the feedback control system to control laser beam power in response to emission spectra data to control the depth of alloying in the workpiece. 6. The method of claim 5 wherein said adjusting uses a feedback control system comprising a controller coupled to receive inputs from said movement system and said laser delivery system. 7. The method of claim 5, wherein said movement system receives imaging data indicative of the position of the laser beam relative to the workpiece. 8. The method of claim 5, wherein said controller receives acoustic signals indicative of the physical dynamics of the alloying process. 9. An apparatus for controlling the depth of laser alloying of a metal workpiece that is moving relative to a laser beam, comprising: a. a laser beam delivery system capable of delivering a laser beam pulse at a desired frequency and power density in response to a beam control signal; b. a movement system capable of causing relative movement between a laser beam emitted from said beam delivery system and a workpiece being irradiated by said beam, said movement occurring at a desired rate, and over desired distance increments, in response to a movement control signal; c. a precursor application system capable of applying a precursor at a desired rate and thickness to the surface of a moving workpiece; d. a feedback control system capable of receiving input signals indicative of one or more measured process parameters, comprising the temperature of the workpiece surface and the emission spectra data, processing said signals, transmitting a beam control signal to said beam delivery system, and transmitting a movement control signal to said movement system, so as to control the depth of laser alloying of a workpiece being moved by the movement system relative to a laser beam being delivered by the beam delivery system; and e. at least one temperature transducer positioned to measure the surface temperature of a workpiece being irradiated by a laser beam, said transducer coupled to said feedback control system to transmit an input signal indicative of surface temperature to said control system. 10. The apparatus of claim 9 wherein said temperature transducer is capable of making a pyrometric temperature measurement. 11. The apparatus of claim 9 further comprising a video imaging device positioned to make a video image of the region of a workpiece being irradiated by a laser beam, said imaging device being coupled to said control system such that video image data can be transmitted to said control system. 12. The apparatus of claim 9 further comprising an emission spectra measuring device positioned to measure an emission spectra emanating from a plasma formed in the surface of a workpiece irradiated by a laser beam, said measuring device being coupled to said control system such that emission spectra data can be transmitted to said control system. 13. The apparatus of claim 9, wherein said beam delivery system comprises an infrared detector capable of measuring fluctuations in laser power, and transmitting a signal indicative of laser power to said control system. 14. The apparatus of claim 9 wherein said precursor application system is capable of applying a precursor at a desired rate in response to an application control signal and wherein said control system in capable of transmitting an application control signal to said application system. 15. The apparatus of claim 9 further comprising a gas delivery system positioned to deliver a gas to the region of a workpiece being irradiated by a laser beam from said beam delivery system. 16. The apparatus of claim 15 wherein said gas delivery system is capable of delivering gas at a controlled flow rate in response to a gas control signal and wherein said control system is capable of transmitting a gas control signal to said gas delivery system. 17. The apparatus of claim 15, wherein the gas delivered by said gas delivery system is a reducing gas. 18. The apparatus of claim 15, wherein the gas delivered by said gas delivery system is a shielding gas.